A number of roller blinds for use in very long window openings may be manipulated synchronously by driving the outermost roller blind at one side and to transmit the rotation from one to the next, there being bearing brackets with bearings provided between the roller blinds. Frequently, the end plugs will engage small pieces of drive shaft that are carried in the bearing brackets.
However, differences in the rolling that have occurred during installation may entail that some of the roller blinds fitted hang lower and cannot be raised completely, because the drive motor stops when the first roller blind has reached its upmost position. There is hence a need to turn a neighbouring roller blind in order that it may be fine-adjusted independently of the others. This must occur by uncoupling the force transmitting element between the roller blind tubes.
An uncoupling between two tubes may occur by sideways shifting of a cylindrical bushing that engages both tubes, in order that the tubes may be turned independently. Such a solution cannot be used, however, when there is fitted a bearing bracket between the tubes. The bearing bracket carries a short piece of shaft between the tubes mentioned and is essential to retain the straightness of the axis of rotation, even though it is long. An uncoupling may be obtained in this case in that a bushing with a grub screw connects one of the roller blind tubes with the piece of shaft. Such a bushing may be loosened by loosening the grub screw, the adjustment may be performed, and the grub screw is tightened again. This is a solution that requires tools and furthermore that the grub screw is accessible, i.e. facing the room in which the roller blind is placed. This means that when adjusting, the roller blind must be lowered until the grub screw is accessible. Furthermore, a grub screw for fine adjustment must work against a cylindrical part of a shaft. However, drive shafts for roller blinds frequently have a polygonous cross section in order to transmit a torque.
Hence there must be a part of a drive shaft that needs special machining in order to provide a cylindrical surface, and this is costly. A lowering in this situation would occur by means of the usual control unit, which is frequently fixed in one place, while the adjustment must occur between the two roller blinds that do not have the same rolled length. The two activities may rarely be performed without the need for the operator to move from one place to the other.
There is hence a need for a fine-adjusting element that is capable of uncoupling a roller blind from a shaft during the fine adjustment and without the use of tools.